Air Source Heat Pumps data sheet

Air Source Heat Pumps use refrigeration technology to provide heat from a condensing unit. The evaporator side of the heat pump absorbs energy from the air outside the house using it as a source of heat for a properties hot water cylinder, radiators or underfloor heating. Designed well, an Air Source Heat Pump will provide all the hot water and heating a property requires for 365 days a year.

Suitable for:

Air Source Heat Pumps are compact and externally situated so are suitable for a wide range of properties. Working at a lower temperature than oil or gas boilers, Air Source Heat Pumps are recommended for well-insulated properties.

They are well-suited to new build properties, in particular those that do not have a gas supply, because the running cost comparisons versus oil boilers are particularly attractive. They are popular with developers building new build homes as they integrate well with underfloor heating.

They also work well in existing buildings that are well-insulated, but the installer must make careful checks whether the existing radiators are big enough to heat the property, and oversized radiators are sometimes required. It is quite common for an existing property that is refitted with an air source heat pump to have underfloor heating fitted downstairs, whilst existing radiators are retained upstairs.

Technical information

Heat Pumps use refrigeration technology to provide heat from a condensing unit. The evaporator side of the heat pump absorbs energy from the air outside the house using it as a source of heat. The efficiency of a heat pump is denoted by its coefficient of performance know as ‘COP’. This is the ratio of energy extracted from the source and energy used by the heat pump itself. Typical COP values for ground source heat pumps are 3.5-4.5, whereas air source heat pumps tend to have a CoP of between 2.5-3.5. With the current mix of fuels for electricity production, using a heat pump produces slightly less emissions compared with conventional gas heating.

There are three types of air source heat pumps; air-to-air, air-to-water and split systems. Air to water pumps are used for heating and hot water by taking heat from the outside air and transferring it to the heating system via a heat pump - this process uses the principles of vapour compression. The air to air heat pumps heat up the air by drawing air into the unit, warming it up and then circulating the heated air around the property via a fan.

Low temperature split systems have two units, one is located outside of the property and another inside. A refrigerant connects the two units and transfers the energy absorbed from the outside air. This allows flexibility in the installation and means the outside unit can be located up to 50m away from the inside unit.

All air source heat pumps must be adequately sized and sited away from obstacles that may obstruct air flow. If the evaporator is inadequately sized or air flow is restricted, the unit may freeze, causing it to go into defrost mode which reverses the heat pump and uses electrical energy to melt the ice. This process reduces the COP of the unit and makes it less fuel efficient. The heat pump should be located outside the house on a sunny wall with plenty of room for airflow. This will also allow the heat pump to be easily accessible for servicing.

Latent heat is present in air temperatures as low as -20 degrees so the UK climate is suitable for an Air Source Heat Pump to heat your home, even on our coldest days.

Hints & Tips

  • For optimum results you need to ensure that the fabric of the building is well insulated and draught proofed.
  • Air Source Heat Pumps can work better in conjunction with the use of underfloor heating systems. They operate at more than 3 times the efficiency of conventional heating systems and as a result help to minimise C02 emissions and reduce the heating costs of your property.
  • Air source heat pumps do not need planning permission from the local council.
  • Air Source Heat Pump can provide you with an income through the Renewable's Heat Incentive (RHI).
  • When installing Air Source Heat Pumps, you need to make sure they are suitable, making sure you have adequate space, they work better when replacing oil and LPG.